As all "global" style guidances, this one suffers from not giving a true picture. The truth is: IT IS IMPOSSIBLE to make a movie that was done on a budget to look like it was done with great financing. If it would be possible, nobody would do it in any other way. Everyone these days is looking to cut costs.
However, lack of budget may be concealed depending on a type of production.
First, if you want make it looking rich, use various camera angles. Use two or more cameras if you can. Don't stay on a single scene more than it can afford in terms of point of interest. Avoid blatant errors like jump frames, sudden change of direction, crossing line etc. If your camera skills aren't perfect, adopt filming style of 50x-60x: keep it simple, make clear cuts and logical final points, DO NOT ZOOM, unless you show emotional change, etc. Watch some movies of the period, adopt culture of the presentation.
Second, use (RF) royalty free footage and sound. There are many to choose from, I like libraries by DVDxDVD and Mproducer, both old and new in Hi-Def, as they are cheap, well shot and can be used for anything you want. For a price of few clips elsewhere you get the entire thing. The RF footage creates illusion of places, locations, effects that otherwise unreachable or very costly to shoot. Green screen is your best friend when it comes to creating value! Think of James Bond movies. In 99% you see a green screen chroma key footage or half screen combinations. Green screen is your magic tool of everything! With little imagination and 5-6 days skills, you can transform park into magic kingdom and your mama in law into Cinderella.
Third. Get good texts!!!!!!! Man it is crucial one! Remember, TALKING IS CHEAP, repeat it until it became part of you. It is much cheaper, both in time and money, than creating animated effects. Good text creates interest, especially if well, artistically delivered. Shooting of a talking actor/talent/voice etc is super cheap. It is just a talking head. It is also easy to shoot and edit. If done well it creates more impact than all cool effect together.
Forth. Get creative. Use change of speed of action, use some time lapse footage, add some color flames here and there, use costumes from old closets, buy cheap hats they all look nice on a camera. In short, bring your element.
Fifth. Sound must be great. Sweeten the audio, especially dialogs. Dialogs must be clear, clean, easy to listen to, well articulated and frame synchronized (remember in "singing in a rain" no-no-no-yes-yes-yes) . Use a music from RF (as I mention before). Avoid too much of voice over music. It sounds moody and can make dialogs hard to understand. Put some great sounding music where appropriate. There are plenty of famous songs from movies that no one remembers.
Six. Do not listen to any advices, including this one.
Hope it helps